Japanese Patent Laying-Open No. 9-215211 (Patent Document 1) discloses a charging system for electric vehicle capable of charging a power storage device of an electric vehicle from a power supply outside of the vehicle in a non-contact manner by electromagnetically coupling a primary coil connected to the power supply outside of the vehicle to a secondary coil connected to the power storage device of the vehicle. This charging system has the secondary coil provided on the underbody of the vehicle.
A recess is formed in a floor of a parking space, with a coil moving apparatus movably supporting the primary coil provided therein. A body of the coil moving apparatus is provided with three magnetic sensors.
In order to charge the power storage device of the vehicle, the vehicle is parked over the recess to excite the secondary coil. Consequently, a position of the secondary coil is detected by the magnetic sensors. Then, the coil moving apparatus is driven based on the detection result, to guide the primary coil to a position where both coils are electromagnetically coupled to each other (see Patent Document 1).
Power transfer using electromagnetic induction, power transfer using a microwave, and power transfer by resonance are known as dominant non-contact power transfer techniques for transferring electric power in a non-contact manner without using a power cord or a power transfer cable.
Resonance is a technique for causing a pair of resonators (e.g., a pair of self-resonant coils) to resonate with each other in an electromagnetic field (near field) to transfer electric power in a non-contact manner through the electromagnetic field, and can transfer large electric power of several kW across a relatively long distance (e.g., several meters) (see Non-Patent Document 1).
Patent Document 1: Japanese Patent Laying-Open No. 9-215211
Patent Document 2: Japanese Patent Laying-Open No. 11-1177
Non-Patent Document 1: Andre Kurs et al., “Wireless Power Transfer via Strongly Coupled Magnetic Resonances,” [online], Jul. 6, 2007, Science, Vol. 317, pp. 83-86, [searched on Sep. 12, 2007], the Internet <URL:http ://www.sciencemag.org/cgi/reprint/317/5834/83.pdf>